After perusing the web for a while,
this quote seems to sum up what I found elsewhere; African Blackwood is a very responsive, excellent tone wood ... Mellow tone and attack. This wood is sought after for high end woodwinds (clarinets, oboes, flutes, etc.) and bagpipes. I've also seen it on a few high end acoustic guitars employed on the back and sides. In reference to it's use in acoustic guitars, I found a
quote that suggests the tone is not as deep as Brazilian Rosewood but not as tight as Mahogany. That quote combined with several others I ran across suggest to me that Blackwood is going to be similar in tone to Rosewood.
All of this is to say that I have absolutely no idea. My guess is that as a top wood it probably doesn't add to the sound as much as Ebony or Coco Bolo would, that it wouldn't have the fundamental clarity of Ebony or the complexity of Coco Bolo; but I'm just guessing. I really have no idea. If cost is no object, it certainly sounds like an interesting idea. One post I read indicated that it is becoming increasingly more difficult to find Blackwood is sizes large enough to make a two piece back for an acoustic guitar. I don't know if any of this is helpful to you or not; but it certainly looks interesting.